Theoretical prediction of the hydrogen-bond basicity pKHB

Ab initio and DFT calculations on around 65 hydrogen bond or Lewis bases and their complexes with hydrogen fluoride have been performed, and a range of calculated properties from both free bases and complexes correlated with pK(HB), an experimental scale of hydrogen-bond basicity, For the entire range of bases, we found that the hydrogen-bond binding Gibbs free energy computed at the B3LYP/631+G(d,p) level of theory linearly correlated with pKHB. Further improvements in the correlation and prediction of pK(HB), were possible with a non-linear fit by considering the hydrogen bonding Gibbs free energy of another possible stereo-isomeric 1:1 complex and/or that of a linear 2:1 complex, which included a second hydrogen fluoride.